1. Field of the Invention
The present invention relates generally to dental hand pieces. More particularly, the invention concerns a dental hand piece and the method of making the same having a novel safety check valve embodied in the housing thereof that positively prevents back flow of bacterial contaminants through the hand piece.
2. Discussion of the Invention
Microbial contamination of dental unit water lines has recently been recognized as being a potentially serious health problem. More particularly, recognition of the substantial biohazards involved in disposing and aerosolizing suspensions of water borne microorganisms, some of them pathogenic, has created considerable concern on the part of the dental profession as well as various federal agencies, including The Centers for Disease Control and Prevention.
Contamination of the dental unit water lines is due in large measure to "suck back" from the open tips of conventional air-water type hand pieces. In this regard, tests have shown that up to 900 micro liters of contaminated oral fluids and other detritus generated during a dental procedure can be drawn up to several feet into the water line of the unit. Additionally, the problem may be further complicated by the occurrence of complex hydra-dynamic phenomena at the exposed tip of the waterline especially when pressurized flow is abruptly stopped leading to the possibility of passive retraction of the contaminated oral fluids.
Several infection control procedures have been suggested in the past which are directed toward mitigating the serious problem of microbial contamination of dental unit waterlines. One of these control procedures suggests the step of a positive discharge of water from the hand piece for several minutes after each dental procedure and at the beginning of the clinic day. However, this procedure has proven to be generally unsatisfactory and, in fact, may lead to an increase in microbial contaminant levels due to the dislodging of flakes of biofilm from the tubing wall during the flushing operation.
Another control approach, which has been suggested by some agencies, involves the use of sterile water during the performance of surgical procedures within the oral cavity. This approach has generally not been adopted by the practicing dentists due to the unavailability of sterile water at the dental surgery situs. Still another suggested infection control procedure involves the use of biocidal rinses or flushes both during and after the dental procedure. However, the use of such biocidal agents typically requires prior approval by the Food and Drug Administration which approval has not readily been obtainable.
In summary, the infection control procedures that have been proposed in the past have been generally ineffective and, until now, the serious problems of microbial contamination of dental unit water lines remains basically unsolved. It is against this background that the present inventor sought to, and did in fact, solve the difficult problem of control of microbial contamination of dental unit water lines.